There are many types of audio amplifiers, including class A, class B, class AB linear amplifiers, and class D also known as switching amplifiers. Each type has many variations with different types of transistors, and there are trade-offs in efficiency, distortion, power levels and noise immunity or rejection for various types of noise. Miniaturization of audio amplifiers and speakers for earbuds imposes specialized constraints for power management, efficiency, size, and operation in environments with electromagnetically coupled noise.